Packaged microelectronic assemblies, such as memory chips and microprocessor chips, typically include a microelectronic die mounted to a substrate (e.g., an interposer board) and encased in a plastic protective covering. The die includes functional features, such as memory cells, processor circuits, and interconnecting circuitry. The die also typically includes die bond pads that are electrically coupled to the internal functional features. The bond pads are then coupled to corresponding first bond pads on the substrate (e.g., with wire bonds or solder balls), and this connection is protected with the plastic protective covering. The first substrate bond pads can be coupled to second substrate bond pads via pathways that are internal to the substrate. The second bond pads can in turn be connected to external electronic devices in which the die is installed.
In some cases, for example, when the microelectronic die includes an image sensor, the die bond pads are positioned on the opposite side of the die from the image sensor and other microelectronic elements. In such cases, the microelectronic die can include multiple through-wafer interconnects (TWIs) that extend through the die so as to electrically connect the microelectronic features located toward one surface of the die with bond pads positioned at the opposite surface of the die. In many cases, the formation of the TWIs and other manufacturing processes are conducted at the wafer level, i.e., prior to singulating individual dies from the wafer. At this point in the manufacturing process, the wafer is relatively thick. After the TWIs are formed, material can be removed from the backside of the wafer using a backgrinding process to thin the wafer prior to singulating the wafer into individual dies. Thinning the wafer reduces the thickness of the individual dies and therefore makes the dies easier to integrate with very compact electronic devices.
One drawback with the foregoing approach is that the wafer can be extremely difficult to handle after it has gone through the backgrinding process. In particular, the wafer can be so thin that it can easily break. One approach to addressing this drawback is to temporarily attach the wafer to a carrier which provides support for the wafer during manufacturing processes that are conducted after the wafer has been thinned and before individual dies are singulated from the wafer.
Existing techniques for supporting the thinned wafer during post-processing steps have also suffered from several drawbacks. For example, adhesives are typically used to temporarily attach the thinned wafer to the carrier during post-thinning operations. However, typical adhesives become soft and undergo a significant reduction in holding power at elevated temperatures (e.g., above about 150° C.). As a result of the temperature characteristics of the adhesive, high temperature processes cannot generally be completed on the wafer once it is attached to the carrier. In particular, the temperature limitations of the adhesive may limit the manufacturer to only certain processes that may be conducted on the wafer while it is attached to the carrier. For example, the manufacturer may be required to employ a low temperature process on the wafer, when a high temperature process would be more efficient and/or effective. Still further, typical carriers are made from a dielectric material, which can trap the heat that may be generated during processes conducted on the thinned wafer. As a result, the wafer may overheat, which can damage or destroy the functional elements of the wafer.